1. Field of the Invention
This invention relates to a striker pin device mounted inside a totally enclosed fuse structure and arranged to pierce one end of the fuse structure upon operation of the fuse thereby to provide a visual indication of the operated condition of the fuse or so as to actuate an auxiliary device such as a switching device.
2. Background of Information
One known type of a fuse striker device is of the spring actuated type wherein a striker pin is seated on a compressed spring that is held in compressed condition by a high resistance strain wire which is electrically connected in shunt with the fuse links. Upon rupture of the fuse links this wire is quickly melted by the current shunted through it. Melting of the high resistance strain wire results in the release of the pin which protrudes through the end of the fuse to provide an indication of the operated condition of the fuse or to actuate a signal or switching device.
Objections to the spring actuated type of striker assembly are due to the high costs and large physical dimensions thereof.
Another known fuse striker is of the so-called pyrotechnic or powder-actuated type wherein a powder charge is ignited by an ignition element to actuate piston means and thus to drive the striker pin into its operated condition.
The disadvantages of the powder actuated device center primarily around the fact that such mechanisms must be constructed with close tolerances to prevent the escape of piston actuating gases. Such constructions are particularly costly and are vulnerable to rough handling since the ignition element is usually high resistance fragile wire which is easily damaged because of its brittle nature.
Another known pyrotechnic or powder-actuated fuse striker is disclosed in U.S. Pat. No. 4,322,706 issuing on Mar. 30, 1982. In the device of U.S. Pat. No. 4,322,706 a striker housing comprising two or more complementary mating sections with a longitudinal groove formed in the face of at least one mating section receives a fragile elongated ignition element. The mating sections effectively close one end of the housing rendering it substantially gas tight. A piston slideable within the housing is operated by pyrotechnic material. The piston has a cup-like configuration with an outwardly flared lip portion which substantially eliminates leakage of propulsion gases between the piston and the housing wall without requiring close machining tolerances for the flared piston and for the inner surface of the housing.
A main disadvantage of the striker pin device disclosed in U.S. Pat. No. 4,332,706 is the fact that the ignition element must be securely fastened to the contact and the contact plate which are, in turn, welded to the bottom of the cup-like piston. As these elements are usually diminutive, the assembly of these components in the cup-like piston oftentimes is difficult in that the cup-like piston provides an extremely small space in which to work.